Hydrogen purification module

ABSTRACT

A compact hydrogen purification module capable of affording high-grade purified hydrogen, easy assembly and easy control of size is disclosed. The module includes a plurality of unit cells. Each of the unit cells includes two metal membranes permeable only by hydrogen, a metal support ring attached between the metal membranes by diffusion bonding to support the metal membranes, and having a radial hole to allow porous plate disposed between the metal membranes to allow the hydrogen to flow therethrough, and a fitting coupled to the metal support ring and having a hole communicating with the hole of the metal support ring to allow the hydrogen to flow therethrough. The individual fittings are connected to each other so that hydrogen collected in the individual fittings is discharged through a hydrogen product line.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a hydrogen purification module,and more particularly to a hydrogen purification module, which iscomprised of unit cells, each having metal membranes permeable byhydrogen, by coupling individual fittings of the unit cells.

[0003] 2. Description of the Prior Art

[0004] A hydrogen purification module is a device for purifying mixedgas containing hydrogen, or low-purity reformed hydrogen, intohigh-purity hydrogen. The hydrogen purification module functions toproduce high-purity hydrogen by selectively extracting only purehydrogen from reformed gas produced by reforming hydrocarbon fuel suchas gasoline, ethanol, methanol and natural gas, low-purity generalhydrogen, or mixed gases containing hydrogen.

[0005] The hydrogen purification module can be used in producinghigh-purity hydrogen from low-purity regular hydrogen, and can be usedas a hydrogen purification module for a small fuel reformer, whichserves to remove impurities such as CO, by being connected to a reformerfor reforming hydrocarbon fuel such as gasoline, ethanol, methanol ornatural gas. The hydrogen purification module can also be applied to asmall sized fuel reforming apparatus of a small sized system forgenerating electrical energy in combination with a fuel cell system, andcan be applied to a small fuel reformer of a fuel cell powered vehicle.

[0006] U.S. Pat. No. 5,498,278 discloses a hydrogen separation membraneand a hydrogen separation module having a hydrogen separation membrane.The hydrogen separation membrane is comprised of a hydrogen-permeablemetal coating layer, a support matrix and a porous layer disposedbetween the metal coating layer and the support matrix. With thehydrogen separation membrane, a plate-and-frame type hydrogenpurification module or a shell-and-tube type hydrogen purificationmodule is produced. Purification of hydrogen in this type of hydrogenpurification module is achieved at high temperatures of 200° C.-1000° C.However, this type of hydrogen purification module has not only heatloss but also a chance of leakage of purified hydrogen due to componentssuch as gaskets. Furthermore, this type of hydrogen purification modulehas a complicated structure and a heavy weight.

[0007] U.S. Pat. No. 5,645,626 discloses a cylindrical hydrogenpurification module. The hydrogen purification module includes an inlet,an hydrogen outlet, a raffinate outlet and a hydrogen-permeablemembrane. In this type of hydrogen purification module, a coating metallayer, a support matrix and an intermediate layer of a flat plate arecommonly formed with central vertical holes. There is the provision of agas-tight seal around the periphery of the holes through a metal coatinglayer of the membrane to prevent the leakage of hydrogen. Hydrogen,permeated through the metal membrane, passes through the hole of thehydrogen-permeable metal membrane. The hydrogen-permeable membrane isprovided with a peripheral hollow, which may be a notch, a slot, aseries of notches or slots, or a truncated section at the perimeterthereof. Such a hydrogen purification module also has disadvantages inthat its operational temperature is limited, it is not suitable togenerate ultrapure hydrogen due to heat loss at flange, and its weightis increased due to the gasket.

[0008] U.S. Pat. No. 5,997,594 discloses a steam reformer withininternal hydrogen purification, which includes a reforming chamberhaving a reformation catalyst for producing reformed gas containinghydrogen from feed gas, and a metal membrane for dividing the reformedgas into byproduct gas and hydrogen gas. The steam reformer is providedwith a tube-shaped hydrogen-permeable membrane.

[0009] As described above, the above-mentioned conventional hydrogenpurification modules have disadvantages in that it is difficult toachieve a compact structure due to their complicated structures, and toachieve high-purity hydrogen, due to leakage of purified hydrogen.Furthermore, conventional hydrogen purification modules have adisadvantage in that components such as gaskets are damaged at thetemperatures required to purify hydrogen, resulting in heat loss.

[0010] In addition, though the conventional hydrogen purificationmodules must be simply and compactly constructed in order to be used ina small fuel reformer for fuel cell powered vehicles, conventionalhydrogen purification modules cannot be compactly constructed because ofcomplicated structures and assemblies.

SUMMARY OF THE INVENTION

[0011] Accordingly, the present invention has been made keeping in mindthe above problems occurring in the prior art, and an object of thepresent invention is to provide a hydrogen purification module which iseasily assembled and compactly constructed without heat loss or leakageof purified hydrogen.

[0012] In order to accomplish the above object, the present inventionprovides a hydrogen purification module which is manufactured byattaching metal membranes, permeable only by hydrogen, to a metalsupport ring by a diffusion-bonding technique to obtain an unit cell,and coupling a plurality of unit cells to each other via fittings, suchas reducers or unions. These hydrogen purification modules can beconfigured into a desired size by arranging the hydrogen purificationmodules in series and/or in parallel by appropriate coupling of thefittings. Since the metal membranes are attached to the metal supportring by diffusion boding, and the unit cells are coupled to each otherby the fittings without graphite or copper gaskets, there is no leakageof hydrogen even at high temperatures, and there is a provision of easyassembly and ultrapure hydrogen, having a purity more than 99.99999%.

[0013] According to an aspect of the present invention, there isprovided a hydrogen purification module comprising: a plurality of unitcells, each of the unit cells comprising: two metal membranes which areselectively permeable only by hydrogen; a metal support ring disposedbetween the metal membranes and attached to the metal membranes at bothits sides by diffusion bonding so as to support the metal membranes, themetal support ring being provided with a radial hole to allow hydrogenpermeated through the metal membranes to flow therethrough; a porousplate disposed between the metal membranes so as to allow the hydrogenpermeated through the metal membranes to flow therethrough; and afitting coupled to the metal support ring, including a holecommunicating with the hole of the metal support ring so as to allow thehydrogen in the porous plate to flow therethrough; wherein theindividual fittings are connected to each other so that hydrogencollected in the individual fittings is discharged through a hydrogenproduct line. The plurality of unit cells may coupled to each other byfittings to construct a unit module, and the individual unit modules maybe arranged parallel to each other.

[0014] According to another aspect of the present invention, there isprovided a hydrogen separation reactor comprising: a housing receivingthe hydrogen purification module; an inlet connected to the hydrogenpurification module to allow mixed gases to be introduced into thehydrogen purification module therethrough; a hydrogen product lineconnected to the hydrogen purification module to discharge purifiedhydrogen by the hydrogen purification module; and a raffinate outlet,connected to the hydrogen purification module, to discharge the residualgases of the mixed gases.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

[0016]FIG. 1 is an exploded perspective view of a unit cell of ahydrogen purification module according to the present invention;

[0017]FIG. 2 is a cross-sectional view of the unit cell of the hydrogenpurification module shown in FIG. 1;

[0018]FIG. 3 is a cross-sectional view of a unit hydrogen purificationmodule achieved by coupling via fittings the unit cells shown in FIG. 2;

[0019]FIG. 4 is a cross-sectional view of a hydrogen purification moduleaccording to the present invention achieved by parallel combination ofthe unit hydrogen purification modules shown in FIG. 3; and

[0020]FIG. 5 is a perspective view of a hydrogen separation reactorreceiving the hydrogen purification module shown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0021] This invention will be described in further detail by way ofexample with reference to the accompanying drawings.

[0022]FIG. 1 is a perspective view showing a pair of metal membranes 10,a metal support ring 20 and a porous plate 30, and FIG. 2 is an enlargedcross-sectional view of a unit cell comprised of the metal membranes 10,the metal support ring 20, the porous plate 30 and a fitting 40. Themetal membranes 10 are selectively permeable only by hydrogen, andinclude Pd membranes, Pd alloy membranes and Pd coated membranes. Themetal membranes 10 may further include composite membranes produced bycoating V, Ni, or alloys thereof, with Pd. An example of such a metalmembrane, which is selectively permeable only by hydrogen, is disclosedin U.S. Pat. No. 5,645,626.

[0023] According to the present invention, the metal membranes 10 arefirst attached to both sides of the metal support ring 20 by diffusionbonding. Interposed between the pair of metal membranes 10 is the porousplate 30, to allow hydrogen to be easily transmitted therethrough and tosupport the metal membranes. The porous plate 30 is made of metal mesheor porous metal.

[0024] Before the metal membranes 10 are attached to the metal supportring 20 by diffusion bonding, surfaces of the metal support ring 20 arepreferably flattened and smoothed by chemical or mechanical polishing.In addition, the metal membranes 10 are scrubbed by a sandpaper having afine grain size to remove oxide films in the metal membranes, and thenprovided with fine scratches to increase surface area, therebymaximizing the hydrogen-permeable area of the metal membranes.

[0025] The metal support ring 20 is formed with a radial hole 21 at itsinner surface, so that hydrogen, which is permeated through the metalmembranes, can pass therethrough. The metal support ring 20 ispreferably, but not exclusively, made of a copper plate.

[0026] The fitting 40 is attached to the metal support ring 20.

[0027] More specifically, the fitting 40 is bonded to the metal supportring 20 by welding 23 or brazing, such that the hole 41 formed at thefitting 40 coincides with the hole 21 of the metal support ring 20, soas to allow the hydrogen passed through the metal membranes to flowtherethrough.

[0028] As shown in FIG. 2, the fitting 40 is formed with a vertical bore44. The fitting 40 is further provided with a hole, which ishorizontally positioned between the hole 21 of the metal support ring 20and the vertical hole 44, to communicate with them. Consequently, thehydrogen, passed through the metal membranes 10, is collected in thevertical hole 44 of the fitting 40 through the hole 21 of the metalsupport ring 20 and the hole 41 of the fitting 40.

[0029] The fitting 40 used in the present invention is provided at oneend with a female threaded part 43, and is provided at the other endwith a male threaded part 42. Accordingly, the fittings 40 can becoupled to each other by coupling of the female and male threaded parts43 and 42. However, the fitting according to the present invention isnot limited to the above-mentioned configuration, and can be constructedinto any other configuration suitable to the present invention. That is,various fittings such as reducers and unions may be used.

[0030] A plurality of unit cells, each of which is comprised of themetal membranes 10, the metal support ring 20, the porous plate 30 and afitting 40, are coupled to each other by coupling the fittings 40 toconstruct a hydrogen purification module. The hydrogen purificationmodule according to the present invention can be controlled in its sizeby selecting the number of the unit cells 100 as required.

[0031] Referring to FIG. 3, there is shown a hydrogen purificationmodule 200. Hydrogen passed through the metal membranes 10 is introducedinto the holes 21 of the metal support rings 20 through the porousplates 30. The hydrogen introduced into the holes 21 is introduced intothe vertical bores 44 through the horizontal holes 41 of the fitting 40.The hydrogen introduced into the vertical bores 44 is collected by thecoupled fittings 40 and is discharged through a hydrogen product line.

[0032] In this hydrogen purification module 200, the spacing definedbetween the unit cells is somewhat large due to the length of thefittings. In order to manufacture a compact hydrogen purification moduleby reducing the spacing between the unit cells, two or more unit modulescan be disposed to be parallel to each other.

[0033] More specifically, as shown in FIG. 4, two or more unit modulesmay be disposed side by side, such that the unit cells 100 of both unitmodules are alternately arranged, so as to fabricate a compact hydrogenpurification module 200′.

[0034] Hydrogen, collected in the fittings of the two or more unitmodules, is merged at one or more hydrogen product lines 50 and senttherethrough. By this parallel arrangement of the hydrogen purificationmodules, it is possible to control the spacing between the adjacent unitcells and the number of the unit cells with respect to a given length ofthe fittings, thereby affording a compact hydrogen purification module.

[0035] Referring to FIG. 5, there is shown a hydrogen separation reactor300, which is provided with the hydrogen purification module accordingto the present invention.

[0036] The hydrogen separation reactor comprises a housing 60 receivingthe hydrogen purification modules, a hydrogen product line 50, an inlet70 for mixed gas, and a raffinate outlet 80.

[0037] In an operation of the hydrogen separation reactor 300, mixedgases, containing hydrogen, general hydrogen or low purity reformedhydrogen, are introduced into the hydrogen separation reactor throughthe inlet 70. The introduced gas is purified by the hydrogenpurification modules received in the housing 60. From the introducedmixed gases, only hydrogen permeates the metal membranes of the hydrogenpurification modules, and the permeated hydrogen is collected in thebores of the fittings of the hydrogen purification modules and isdischarged through the hydrogen product line 50. Residual gases, thoseother than the hydrogen, are collected and then discharged through theraffinate outlet 80.

[0038] In this way, as hydrogen, which has selectively permeated throughthe metal membrane, flows into the bores 44 of the fittings 40 throughthe holes 21 of the metal support rings 20 bonded to the metal membranes10 and the holes 41 of the fittings 40 welded to the metal support rings20, there is no fear of leakage of hydrogen, thereby affordinghigh-grade purification of hydrogen.

[0039] As described above, the present invention provides a hydrogenpurification module, which can be selectively permeable to hydrogencontained in fixed gas, and can afford high-grade purification ofhydrogen without any leakage of hydrogen.

[0040] Furthermore, since a plurality of hydrogen-permeable metalmembranes can be easily coupled to each other by fittings allowingpermeated hydrogen to pass therethrough, the hydrogen purificationmodules can be easily and compactly fabricated, and the size of thehydrogen purification module and the spacing between the unit cells canbe easily controlled.

[0041] In addition, the hydrogen purification module according to thepresent invention can be used in a small sized apparatus for generatingultrapure hydrogen, and which also serves to remove impurities such asCO, by connection to a reformer for reforming hydrocarbon fuel such asgasoline, ethanol, methanol or natural gas. The hydrogen purificationmodule can also be applied to a small sized fuel reforming apparatus ofa small-sized system for generating electrical energy or a fuelcell-powered vehicle, by combination with a fuel cell system.

[0042] Although a preferred embodiment of the present invention has beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

What is claimed is:
 1. A hydrogen purification module comprising: aplurality of unit cells, each of the unit cells comprising: two metalmembranes which are selectively permeable only by hydrogen; a metalsupport ring disposed between the metal membranes and attached to themetal membranes at both its sides by diffusion bonding so as to supportthe metal membranes, the metal support ring being provided with a radialhole to allow hydrogen permeated through the metal membranes to flowtherethrough; a porous plate disposed between the metal membranes so asto allow the hydrogen permeated through the metal membranes to flowtherethrough; and a fitting coupled to the metal support ring, includinga hole communicating with the hole of the metal support ring so as toallow the hydrogen in the porous plate to flow therethrough; wherein theindividual fittings are connected to each other so that hydrogencollected in the individual fittings is discharged through a hydrogenproduct line.
 2. A hydrogen purification module comprising: two or moreunit hydrogen purification modules, each consisting of a plurality ofunit cells, each of the unit cells comprising: two metal membranes whichare selectively permeable to only hydrogen; a metal support ringdisposed between the metal membranes and attached to the metal membranesat both its sides by diffusion bonding so as to support the metalmembranes, the metal support ring being provided with a radial hole toallow hydrogen permeated through the metal membranes to flowtherethrough; a porous plate disposed between the metal membranes so asto allow the hydrogen permeated through the metal membranes to flowtherethrough; and a fitting coupled to the metal support ring andincluding a hole communicating with the hole of the metal support ringso as to allow the hydrogen in the porous plate to flow therethrough;wherein the individual fittings of the plurality of unit cells areconnected to each other to construct the unit module, and two or moreunit modules are disposed parallel to each other, thereby allowinghydrogen, collected in the individual fittings of the two or more unitmodules, to be discharged through a hydrogen product line.
 3. Thehydrogen purification module as set forth in claim 2, wherein the numberof the unit modules equals
 4. 4. The hydrogen purification module as setforth in any of claims 1 to 3, wherein the attachment of the metalsupport ring and the fitting is achieved by welding or brazing.
 5. Thehydrogen purification module as set forth in any of claims 1 to 3,wherein the fitting is a reducer or a union.
 6. A hydrogen separationreactor, comprising: a housing receiving the hydrogen purificationmodule of any of claims 1 to 3; an inlet connected to the hydrogenpurification module to allow mixed gases to be introduced into thehydrogen purification module therethrough; a hydrogen product lineconnected to the hydrogen purification module to discharge purifiedhydrogen by the hydrogen purification module; and a raffinate outlet,connected to the hydrogen purification module, to discharge the residualgases of the mixed gases.